The present invention relates to a sealing arrangement for the attachment of a side plate often used in connection with a pump volute of a centrifugal pump and an attachment screw used therewith.
A centrifugal pump comprises, as known, mainly a so-called volute with a suction opening, a discharge opening, and an impeller rotating inside the volute. Since the efficiency and capacity of the pump are substantial both for the manufacturer, seller and especially for the end user, the clearances between the impeller and the volute must be optimal, in other words in most cases as small as possible. By using modern production methods, it is possible to manufacture optimal clearances in new pumps. However, when pumping even slightly erosive fluids, such as different suspensions, especially the edges of the impeller vanes facing the volute are subjected to wearing, whereby the clearance thereof to the front wall of the volute increases and the efficiency of the pump is reduced. To correct the disadvantage, for example, the front wall of the pump volute facing the impeller vanes is made adjustable. To enable this, a removable side plate is arranged at the front wall of the volute, the position of which side plate may be adjusted in the axial direction of the pump.
The adjustable side plate of the volute of a centrifugal pump is attached to the pump volute with at least three screws enabling the adjustment. The side plate is sealed in accordance with the prior art as illustrated in FIG. 1 by two O-rings, of which one is located at the outer rim of the side plate and the other at the diameter of the inner cylindrical surface of the side plate. The O-rings seal the side plate both at the pressure side of the pump and at the suction side so that the adjustment screws, which function also as attachment screws, are not normally in contact with the liquid to be pumped. If the O-rings leak for some reason, the liquid to be pumped leaks to the back side of the side plate and the adjustment screws get into contact with the liquid. This is not as such detrimental, but a problem arises because the liquid to be pumped is able to leak through the openings arranged for the adjustment or attachment screws in the volute to the outside of the pump. There are, of course, O-rings manufactured of modern materials, which rings could be used in the above-described positions, but as they are large rings, they are almost as expensive as the rest of the pump. Because of the high price, such a construction is not competitive on the market.